Fluid pressure producing device



Aug. l, 1944. E. F. LowEK'E FLUID PRESSURE PRODUCING DEVICE Filed Nov. '7, 1941 Patented Aug. l,

UNITED 'STATES PATENT oFFlcE FLUID PRESSURE PRODUCING DEVICE Erwin F. Loweke, Detroit, Mich., assignor to Hydraulic Brake Company, Detroit, Mich., a corporation of California I Application November 7, 1941, Serial No. 418,267

claims. (cl. so-54.6)

This invention relates to fluid pressure braking systems, and more particularly to fluid pressure producing devices therefor.

The invention comprehends a uid pressure therein supporting a pair of piston heads, one for.

each chamber, the forward piston head being freely-supported for limited movement of adjustment relative to the-other'piston head.

Another object of the invention is to provide a compound cylinder comprising a large cylinder and a small cylinder, a piston reciprocable in each vof the cylinders, and means providing passage of fluid around the piston reciprocable in the small cylinder when the pistons are in retracted position.

Another object of the invention is to provide a fluid pressure producing device including communicating large and small cylinder chambers, a piston reciprocable in each of the cylinders, means loosely coupling the pistons together for .joint'reciprocation and to permit limited axial or vertical movement of the piston reciprocable in the small cylinder relative to the other piston. A meritorious characteristic is that the small piston is suspended in the large cylinder by said coupling means when in retracted position, and means is provided at the entrance to the small cylinder cooperating to align the small piston therewith upon the initial advance stroke of the pistons. A further characteristic is that the piston mechanism is operable to entirely withdraw the small piston from its cylinder, and said piston controls the communication between the two cylinder chambers.

A feature of the invention is the provision of a' compound piston comprising a small piston and a large piston, said large piston -having means adapted to receive and loosely support the small piston. l

Other objects and advantages of the invention will appear from the following description taken in. connection with the accompanying drawing forming a part of this specification, and in which- Fig. 1 is a schematic view of a fluid pressure braking system embodying the invention;`

Fig. 2 is a vertical sectional view of the fluid pressure producing device; and

Fig. 3 is an enlarged sectional view illustrating the high pressure piston structure.

Referring to the drawing for more specic details ofthe invention, IIl represents generally a fluid pressure producing device including a reservoir I2 having a lling opening I4, normally closed as by a plug I6 provided with openings I8 for venting the reservoir to the atmosphere. The plug I6 has therein a perforated diaphragm 20, and a baille plate 22 depended from the diaphragm serves to inhibit surging uid from splashing through the openings I8.

A cylinder 24 at the base of the reservoir includes a large chamber 26 and a relatively small chamber 28 arranged substantially concentrically to, in direct communication with, and forward of the large chamber, and providing at its junction therewith an annular shoulder 36. The cylinder is provided with-a taper 32 between the shoulder and chamber 28, the purpose of which will hereinafter appear.

The large chamber 26 is provided with spaced ports 34 and 36 providing communication between the chamber 26 and reservoir I2. small chamber 28 has a head 38 provided with a discharge port 40 controlled as by a two-way valve 42.

A piston 44 reciprocable in the large chamber 26 is held against displacement by a washer 46 seated yon an annular shoulder in the wall of the cylinder 24 adjacent the open end thereof and secured in place by a retaining ring 48 tted in a groove in the wall of the cylinder. The piston 44 includes a head 50, a reduced body portion 52, providing in conjunction with the cylinder an annular chamber `54 communicating with the reservoir by way of the port 34, a central axially extended sleeve 56, and a skirt 58.

The head 50 of the piston 44 has a plurality of spaced passages therethrough providing communication between the annular chamber 54 and that portion of the cylinder forward of the piston, and a sealing cup 62 seated on the head of the piston forcontrol of the passages is held against displacement by a spring 64 interposed between the cup and the annular shoulder 30. I'he spring 64 also serves to return the piston 44 to its retracted position. t

A hollow plug 66 threaded or otherwise suitably secured in the sleeve 56 provides in con- Junction with the sleeve 56 of the piston 44 a The chamber 68 communicating with the annular chamber 64 by way of passages 10, in the body portion of the piston 44. The skirt of kthe piston has seated thereon a sealing cup 12 for inhibiting 'seepage of fluid from the annular chamber 64 past the piston.

Suitably mounted in a socket in the back of the piston 44 is a thrust pin 14 and on the other end of the thrust pin is a coupling 'I6 connected by a flexible boot 18 to the open end of the cylinder 24 for the exclusion of dust and other foreign substances. A rod 80 has one of its ends connected to the coupling 16 and its other end pivotally connected to a foot pedal lever 82, rockable on a stub shaft 84 and connected by a retractile spring 86 to a fixed support 88.

A relatively small piston 80 of slightly less diameter than chamber 28 and adapted to be reciprocable therein has a head 82 and a rearwardly extended sleeve 84. The sleeve 94 is loosely supported in a groove 86 of plug 66, so `as to provide for a slight vertical and axial movement of piston 80. The groove 86 is formed by the spinning of a collar 98 over the sleeve 94, thus preventing the piston 80 from being separated from the plug 66. The plug has a port therethroughproviding communication between the chamber 26 and chamber 68.

The head 82 of the 'piston 90 has a plurality of passages |02 therethrough and is also provided with an inner annular groove |04 for the reception of a sealing cup |06 so as to seat and firmly hold the cup on the head of the piston.

The sealing cup |06 is adapted to control lthe passages |02 and -additionally provides the pressure seal within chamber 28 during a compression stroke of the piston. The tapered section cylinder and the loose-jointed connection of the piston 80 to the piston 44 permits of slight variances in concentric alignment of the bores of chambers 26 and 28 `without any loss of eiiective pressure producing. The tapered section in providing communication between the chambers when the pistons are in their retracted position eliminates the necessity ofa port in the cylinder wall for such communication. Consequently, the sealing cup |06 is not subjected to wear as is ordinarily the case wherein a sealing cup under pressure has to close off a port in the cylinder wall.

A spring-pressed ball valve |08 in the chamber 68 normally closes off communication between chambers 26 and 68, provided by port |00. A plunger ||0 reciprocable in the sleeve 94 of piston 80 has a head ||2 abutting the sealing cup |06, and an extension ||4 bearing against the ball valve |08.

A fluid pressure delivery line or conduit ||6 suitably connected to the discharge port 40 has branches connected to fluid pressure actuated motors ||8 preferably arranged in pairs, one pair for actuating the brakes associated .with the front wheels of a motor vehicle and another pair associated with the rear wheels of the vehicle.

The brakes may be of any preferred type. As shown, each of the brakes includes a fixedsupport or backing plate |20, a rotatable drum |22 associated therewith, a pair of friction elements or shoes |24 pivoted on the backing plate cooperating with the drum, a retractile spring |26 connecting the shoes, and a motor corresponding to the fluid pressure motor ||6 mounted on the backing .plate between the shoes and connected thereto foractuating the shoes into engagement with the drum against the resistance of the retractile spring.

In a normal operation, upon depressing the foot pedal lever 82 force is transmitted therefrom through the thrust pin 14 to the piston 44. resulting in movement of the piston structure on its compression stroke, and also advancing piston 88.

During the initial movement of the pistons 44 and 90 on the compression stroke, the sealing cup 62 on the piston 44 closes the port 26, and the sealing cup |06 on the piston 80 enters chamber 28 and aligns piston 80 with the chamber, and, thereafter, as the pistons advance, fluid in the chamber 26 is displaced therefrom through the passages |02 past the sealing cup |06 into the chamber 28, thence past the valve 42, through the discharge port 40, and fluid pressure delivery pipe ||6 into the fluid pressure actuated motors H8, causing energization of the motors with the resultant actuation of the friction elements |24 into engagement with the drums |22 against the resistance of the retractile springs |26 to effectively retard rotation of the drums.

As the pistons 44 and 90 are further advanced,

with a consequent increase in pressure, the ball i valve |08, loaded to a predetermined pressure,

cracks due to the fluid pressure on the sealing cup |06 being transmitted through the head ||2 of the plunger I|0 and its extension ||4, thereby unseating the ball I 08. The fluid .pressure in the large chamber is thereby relieved and a portion of the fluid is returned from the large chamber 26, through the port |00, the chamber 68, the passages 10, the annular chamber 54, and port 34, to the reservoir I2.

Upon release of the applied force, the foot pedal lever 82 is returned to its retracted position under the influence of the retractile spring 86. This results in retracting the thrust pin '|4 and release of the piston 44 and return of the pistons 44 and 90 to retracted position under the influence of the spring 64. Together with the Uvrelease ,of thepistons 44 and 90, the springpressed ball valve moves to its closed position.

As the pistons 44 and 90 return to their retracted positions, a partial vacuum is created in chamber 28 forward of the piston head 92, resulting in drawing fiuid from the reservoir through the port 34 into the chamber 54, through the passages 60, past the sealing cup 62, into the chamber 26, thence through the passages |02 in the piston 90 and past the sealing cup |06 into the chamber 28, completely filling the chamber. During this operation fluid is returning to the chamber 28 from the fluid pressure actuated motors I6 a'nd the uid pressure delivery pipes connecting the motors to the cylinder 24 under the influence of the retractile springs |26 connecting the friction elements of the respective brake structures. With the return of the fluid from the motors and fluid line, the chamber 28 may receive a quantity of fluid in excess of its capacity, and under this condition the excessive fluid is displaced therefrom into lchamber 26 through the tapered section 32 of the cylinder, past ythe sealing cup 62 into chamber 26. T he fluid thus returned to the chamber 2| is then displaced therefrom through port II into the reservoir I 2.

While this invention'has been described in connection with certain specific embodiments, the principle-involved is susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended'claims.

Having thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is:

l. A fluid pressure producing device comprising -a cylinder including a large chamber and a small chamber, a piston reciprocable in each of the chambers, socket means coupling the pistons together and normally supporting the pischamber, means coupling the pistons to permit angular movement of the small piston relative to the large piston, said small piston being spaced apart from the small chamber when in retracted ton of the small chamber within the large chamber to so provide direct communication between the chambers, and means adapted to align.,the small piston with the small chamber upon advance of the pistons. 2. A fluid pressure 'producing device comprising a cylinder including a large chamber and a small chamber, a large piston reciprocable in the large chamber, asmall piston reciprocable in the small chamber having a sealing cup on its head, socket means cla-191118 the pistons together,

and a tapered bore section in the small chamber cooperating with the sealing means on the small piston to provide a channel communication between the chambers when the pistons arein retracted position and for aligning the small piston with .the small chamber upon advance of the piston. l

3. A iluid pressure producing device comprising a cylinder including a large and a small chamber, a large piston reciprocable in the large chamber, a small piston reciprocable in the small position, and a tapered bore in the entrance vof the small chamber adapted to align the small piston with the small chamber upon initial actuation thereof.

4. A iluid pressure producing device comprising a pair of communicating cylinder chambers arranged substantially in line, piston mechanism supporting a pair of piston heads reciprocable therein, one head for each cylinder chamber, the' forward piston head being universally jointed to the other piston head for limited transverse movement relative thereto, the piston mechanism being reciprocable to withdraw the forward piston head entirely from its chamber to provide communication between the chambers, and a taforward chamber being shaped to guide the forward piston head therelnto as it approaches 5 saidv chamber, and to provide communication between the chambers when the forward piston is retracted from its chamber.

F. LOWEKE, 

